Multiple extrusion apparatus

ABSTRACT

An extruding apparatus wherein a die-head containing dies for forming two or more layers of thermoplastic material, such as on a core passing through the head, is supplied with material by as many extruder barrels as there are layers. The barrels are connected to the die-head at different points, one of the barrels being fixed to the die-head and the other barrel or barrels being connected to the die-head by a connector which compensates for thermal expansion of the barrels and die-head. This connector has a telescoping component and a universal joint component to compensate for thermal expansion in any direction.

llnited States atet Nelson 1 MULTIPLE EXTRUSION APPARATUS [72] lnventor:Alden W. Nelson, West Mystic,

Conn.

[73] Assignee: Crompton & Knowles Corporation, Worcester, Mass.

22 Filed: Nov. 30, 1970 21 Appl. No.: 93,675

1 Sept. 19, 1972 1,100,002 6/1914 Van Ness ..l8 13 H/ 2,732,588 l/1956Myers ..18/13 H 3,447,204 6/1969 Lainson 1 8/14 P Primary ExaminerRobertL. Spicer, Jr. AttorneyHoward G. Garner, Jr.

[5 7] ABSTRACT An extruding apparatus wherein a die-head containing diesfor forming two or more layers of thermoplastic material, such as on acore passing through the head, is supplied with material by as manyextruder barrels as there are layers. The barrels are connected to thedie-head at different points, one of the barrels being fixed to thedie-head and the other barrel or barrels being connected to the die-headby a connector which compensates for thermal expansion of the barrelsand die-head. This connector has a telescoping component and a universaljoint component to compensate for thermal expansion in any direction.

11 Claims, 6 Drawing Figures MULTIPLE EXTRUSION APPARATUS BACKGROUND OFTHE INVENTION to the manner in which the various extruder coml ponentssuch as extruder barrels and crosshead are arranged and interconnectedto accommodate for thermal expansion of the components.

Thermal expansion has always been a factor to be considered in plasticextrusion machinery. The extent of expansion depends on the temperaturesinvolved and the length of the extruder screw and barrel. With smalllightweight extruders, the total expansion is not particularlybothersome. With single extruders, those in which a single layer ofthermoplastic material is extruded directly from the barrel through adie affixed to the outlet end thereof, thermal expansion is notgenerally a problem. The inlet end is fixed and the outlet endcontaining the die moves with respect to a base. If the extruder is usedfor insulating a cable, the die or outlet end of the extruder barrel isaligned with the the cable when in the hot or expansive condition.

There are special extruder arrangements wherein it is desired tomaintain the exit end of the barrel at a fixed location. One sucharrangement is shown in US. Pat. No. 3,372,434 to J. W. Hendry. In thispatent, an extruder barrel feeds material to a separate materialconsuming device via a conduit, one end of which is fixed thereto andthe other end of which is connected to the extruder barrel by an axialslip joint which allows for axial expansion of the conduit withoutdisturbing the relative spacing of the extruder barrel and materialconsuming device. In the majority of cases, it is preferred to have theentrance end of the extruder barrel fixed. When two or more layers ofthermoplastic material are formed within one material consuming deviceor die-head, a separate extruder barrel is employed for supplyingmaterial for each layer. If two layers are applied, one of the barrelshas to be located at an angle to the extruding axis of the die-head.Arrangements of this type present a special thermal expansion problemwhich cannot be handled in the usual manner, since the thermal expansionof both extruder barrels has to be dealt with. Thermal expansion of thedie head and extruder barrels may cause misalignments of the extruderbarrels with respect to the die-head.

The problem of thermal expansion becomes particularly acute in apparatusfor applying two layers of material on a core such as electrical wire.The wire or core is drawn through the die-head, which contains a die foreach layer to be applied. The die-head for a wire insulating extrusionapparatus is generally referred to as a cross-head, and the insulatingmaterial is supplied from an extruder barrel for each layer. The barrelsare connected to the cross-head at an angle to the longitudinal axis ofthe wire and at different points. If the barrels are located on oppositesides of the cross-head, their expansions are added, and since thebarrels are connected to the cross-head at different points, thecross-head is caused to pivot about a point between these two points.This causes skewing or misalignment of the cross-head with respect tothe longitudinal axis of the wire and also misalignment between thecrosshead and each barrel.

If the barrels are connected to the same side of the die-head, expansionis in the same direction but the use of different size barrels, as issometimes the case, would lead to a change in angle of the die-headalong its longitudinal axis. In most cases, the size of the barrelswould prevent them from being disposed parallel to 0 each other on thesame side of the die-head, creating additional deflection problems.

Whether both barrels are on the same side or one opposite sides of thedie-head, thermal expansion of the die-head itself will change thedistance between the points where the barrels are connected to thedie-head, causing the barrels to bend or deflect. This condition maylead to breakage or leaking.

The same thermal expansion problems may exist with a straight die-headwherein the die-head is applied directly to the end of one extruderbarrel which supplies material for a first layer and a second extruderbarrel may be disposed at an angle to the die-head for supplyingthermoplastic material for a second layer. With this arrangement, eachbarrel will be deflected by the thermal expansion of the other.

SUMMARY OF THE INVENTION It is a principal object of the presentinvention to provide apparatus for extruding multiple layers ofthermoplastic material without any of the above-described problemsassociated with thermal expansion.

The principal object of the invention is accomplished by apparatus inwhich a cross-head is fixed to one of the extruder barrels and attachedto the other barrel through expansion compensating means in whichexpansion of the barrels along their longitudinal axes is accommodatedby allowing the entrance end of the other barrel to move longitudinallyor, preferably, to employ a telescoping connection between the barreland the cross-head. This telescoping connection also utilizes twouniversal joints to accommodate thermal expansion of the cross-head.Expansion of all components can be compensated for by this lastdescribed connection between one of the barrels and the crosshead. Bymaintaining both barrels stationary, at least with respect to theirentrance ends, expansion of the barrel which is fixed to the cross-headwill cause the cross-head to move relative to the longitudinal axis ofthe core. In this case, the apparatus is adjusted or set up so that thecross-head and the core are in the proper relationship while theapparatus is in the hot or operating condition.

It is also possible to arrange one of the extruder barrels so that itslongitudinal axis is parallel with that of the cross-head and isconnected to the cross-head by the previously described thermalexpansion compensating means. This extruder barrel and the cross-headmay be disposed so that the longitudinal expansion of the cross-headwill subtract from that of the barrel but, since the extruder barrel islonger than the cross-head, the barrel will expand more and thedifference in expansion between it and the cross-head will beaccommodated by the two universal joints which form part of theconnector.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood from a reading of the following description in conjunctionwith the accompanying drawings in which:

FIG. 1 is a plan view of the invention, major portions of which are insection;

FIG. 2 is a section of a first modification of the thermal expansioncompensating means;

FIG. 3 is a section similar to FIG. 2 showing a second modification ofthe thermal expansion compensating means; and

FIGS. 4 6 are diagrammatic views illustrating the invention as appliedto different extruder arrangements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1,the preferred form of the invention is shown as applied to an extruderset-up for applying two layers of thermoplastic material to a core. Thecore is indicated at 10 and passes through a cross-head 12, in thedirection of arrow 13, within which are located first and second dies 14and 15 for forming first and second layers, respectively. The diesthemselves need not be of any particular type of construction and may beof any type well known in the art.

The first extruder barrel, generally indicated at 16, has an outlet end18 which is rigidly attached to crosshead 12 so that it supports same. Asecond extruder barrel, generally indicated at 20, has an outlet end 22which is attached to cross-head 12 through thermal expansioncompensating means generally indicated at 24.

The second extruder barrel is shown in FIG. 1 with its longitudinal axisparallel to the longitudinal axis of the cross-head, but it may bearranged so that its longitudinal axis was at a right angle to thelongitudinal axis of the cross-head or at any angle with respect to thecross-head.

Thermoplastic material, indicated at 26, is introduced from the firstextruder into the cross-head at a first point in the crosshead which isupstream of the direction of travel of the core 10. Thermoplasticmaterial, indicated at 28, from the second extruder is introduced intothe cross-head at a point in the crosshead which is downstream of thefirst point with respect to the direction of core travel.

Expansion compensating means 24 includes a first connector generallyindicated at 32 which has a ballshaped portion 33 and an elongatedportion 34 which is fixed to the end 28 of barrel 20. Connector 32 alsohas a bore 35 which extends completely through the connector and whichcommunicates with a bore 36 in end 28. Means 24 also includes a secondconnector generally indicated at 38 which has a ball-shaped portion 40and an elongated portion 42 which is slidable within a sleeve 44 incross-head 12. Connector 38 has a bore 46 extending completelytherethrough which communicates with a die passage 48 via sleeve 44. Theend of portion 42 which extends into sleeve 44 has an inside bevel 50which forms a thin deflectable wall at the very end thereof to effect aseal against the inside wall of sleeve 44 by pressure from within bore46. Portion 42 thereby forms a telescoping connection with sleeve 44 andyet by virtue of bevel 50 maintains a sealed relationship therewith.Compensating means 24 also includes a coupling assembly 52 fashioned asa unit, as shown in FIG. 1 to form sockets S4 and 56 at opposite endsthereof for receiving ball-shaped portions 33 and 40, respectively.Coupling member 52 has bore 58 which communicates with bores 35 and 46.

In operation, thermoplastic material 26 is extrude from an outletopening 60 of end 18 into a die passageway 62 in cross-head 12 to form afirst layer 26 on core 10. Thermoplastic material 28 is extruded frombore 36 in end 22 through bores 35, 58 and 46 and into die passageway 48to form a second layer 28 over layer 26. During operation, all of theelements shown are heated by heaters, not shown, to maintain thethermoplastic material in a fluid condition. Thermal expansion of barrel16 has the effect of moving cross-head 12 in the direction of arrow 64and thermal expansion of outlet end 22 together with expansionofcompensating means 24, although slight, has the effect of moving portion42 of connector 38 in the direction of arrow 66, which is in theopposite direction of arrow 64. Both of the motions indicated by arrows64 and 66 are compensated for by the sliding of end 42 within sleeve 44.If the longitudinal axis of barrel 20 were disposed at a right angle tothe longitudinal axis of the cross-head, as shown in FIG. 4, the motionin the direction of arrow 66 would be greater but would still beaccommodated by the sliding of portion 42 within sleeve 44. Thennalexpansion of the cross-head along its longitudinal axis causes thedownstream end thereof to move in the direction of arrow 68 since thecross-head is fixed to extruder barrel 16 at its upstream end. Thermalexpansion of barrel 20 will cause the outlet end thereof to move in thedirection of arrow 70, which is in the same direction as arrow 68. Sincebarrel 20 is longer than the cross-head, the resulting expansion thereofis greater than for the cross-head and the difference is compensated forby a clockwise rotation, as viewed in FIG. 1, of coupling member 52around ball-shaped portions 33 and 40.

If the longitudinal axis of barrel 20 were disposed at a right angle tothe cross-head, the thermal expansion of the cross-head along itslongitudinal axis would be compensated for by a counter-clockwiserotation, as viewed in FIG. 1, of compensating means 24 aroundball-shaped portions 33 and 40. In fact, the barrel 20 could be disposedin any angle with respect to the cross-head and the effect of itsthermal expansion will be accommodated by expansion compensating means24. If cross-heads having die means for forming more than two layers areused, additional extruder barrels may be attached to the cross-head bycompensating means such as 24.

As shown in FIG. 4, an arrangement is shown wherein the barrels l6 and20 are arranged on opposite sides of the cross-head and at right anglesthereto. Expansion of the barrels 16 and 20 and the cross-head 12 is inthe direction of the arrows 16a, and 20a and 12, respectively.Compensating means 24 accommodates thermal expansion of both barrels inthe direction of arrows 16a and 20a by sliding into cross-head 12 andexpansion of the cross-head in the direction of arrow through itsuniversal joint.

FIG. 5 illustrates an arrangement wherein both barrels are connected tothe same side of the cross-head but at different angles thereto becauseof spacing problems. Expansion of the barrels l6 and and cross-head 12are indicated by the arrows 16b, 20b and 12b, respectively, and it canbe seen that a portion'of the expansion of barrel 20 will be in thedirection of expansion of barrel 16. Compensating means 24 willaccommodate any difference in expansion between the two barrels in thedirection of arrow 16b. The remaining component of motion due toexpansion of barrel 20 will be in a direction opposite to that of arrow12b which would tend to cause greater misalignment than would beexpected from the expansion of cross-head l2 alone. Compensating means24 will pivot in a manner previously described to accommodate for thismisalignment.

FIG. 6 illustrates an arrangement wherein the diehead is a straight-headindicated at 12 and attached directly to the end of a first extruderbarrel indicated at 16. Straight-head 12 contains a die for forming afirst layer from thermoplastic material supplied from barrel 16' and diefor forming a second layer from thermoplastic material supplied from asecond extruder barrel indicated at 20 and attached to straight-head 12'by a compensating means 24' which is identical to previously describedmeans 24. Expansion of barrel 20' will be in the direction of arrow 20cand will be compensated for by the sliding of means 24' within head 12'.Expansion of barrel 16 in the direction of arrow 160 will beaccommodated by the universal point portion of means 24.

DESCRIPTION OF FIRST MODIFICATION A modified expansion compensatingmeans, generally indicated at 71, is shown in FIG. 2. Means 71 includesa first connector 72, a second connector 74 and a coupling member 76.Connector 72 also has a bore 80 which extends therethrough andcommunicates with bore 36 in end 22. Connector 74 has an elongatedportion 82 which is similar to portion 42 and extends into sleeve 44 toform a telescoping connection therewith. Connector 74 also has anenlarged portion 83 which contains a socket 84, part of which is formedby a holding ring 81', and a bore 85 which extends therethrough. The endof portion 82 terminates within sleeve 44 and has an inner bevel 86which is similar to bevel 50 for effecting a seal with sleeve 44.

Each end of coupling member 76 has a ball-shaped portion indicated at 87and 88 which fit into sockets 79 and 84, respectively. Coupling member76 also has a bore 89 extending therethrough which communicates withbores 80 and 85, as shown in FIG. 2. Compensating means 71 functions ina manner similar to compensating means 24 by allowing for relativemotion of end 22 of barrel 20 and cross-head 12 due to thermalexpansion.

DESCRIPTION OF SECOND MODIFICATION Referring to FIG. 3, a secondmodification of an expansion compensating means is indicated generallyat 90 which includes a first connector 91, a second connector 92 and acoupling member 93. Connector 91 has a ball-shaped portion 94 at one endthereof which fits into a socket 95 formed in the end 22' of the secondextruder barrel 20. End 22 is similar to end 22 except for the socket95, part of which is formed by a holding ring 96 which is screwed ontothe end of 22'. The other end of connector 91 has an elongated portion97 which is slidable within a sleeve-like portion 98 of coupling member93 to form a telescoping relationship therewith. A bore 99 extendsthrough connector 91 and is connected to a bore 36' in outlet end 22.The end of elongated portion 97 terminates within sleevelike portion 98and has an inner bevel 100 which is similar to bevel S0 for forming aseal against the inner wall of portion 98.

Connector 92 has a ball-shaped portion 102 at one end thereof which fitsinto a socket 104 in cross-head 12 which is similar to cross-head 12except for the manner in which the compensating means is connectedthereto. A ring 105 similar to 96 forms part of socket 104. The otherend of connector 92 is threaded into coupling member 93 and has a bore106 which communicates with an opening 107 into cross-head l2 and a bore108 in coupling member 93 which is defined by inner wall 101.Thermoplastic material is extruded from bore 36 through bores 99, 108and 106 into opening 107 in cross-head 12'. Ball and socket combinations102,104 and 94,95 form pivoted joints for expansion compensating means90 with cross-head 12' and end 22', respectively. These pivoted jointstogether with the telescoping connection of 97 and 93 allow for relativechange in position of the cross-head and end 22 of the extruder barrelfrom thermal expansion thereof.

Having described the invention, what is now claimed 1. Apparatus forextruding multiple layers of a thermoplastic material comprising:

a. a die-head having dies for forming each of said layers;

b. a first extruder barrel fixed to said die-head for supplyingthermoplastic material to said die-head at a first point;

c. a second extruder barrel for supplying thermoplastic material to saiddie-head at a second point; and

, d. thermal expansion compensating means connecting said secondextruder barrel to said die-head to permit expansion along thelongitudinal axis of said die-head.

2. The apparatus as described in claim 1 wherein said thermal expansioncompensating means comprises:

a. a first connector connected to said second extruder barrel;

b. a second connector telescopically mounted to said die-head; and

c. a coupling member pivotally connected at one end to said firstconnector and at its other end to said second connector.

3. The apparatus as described in claim 2 wherein said telescopicconnection comprises a sleeve and an inner tubular member arranged in aclose sliding fit within said sleeve and terminating therein, theterminating end of said inner member being beveled on the inside foroutward deflection from pressure within said inner tubular member andfor forming a pressure seal against the inner surface of said sleeve.

4. The apparatus as described in claim 2 wherein the pivotal connectionsfor said coupling member are ball and socket joints.

5. The apparatus as described in claim 4 wherein each of said ball andsocket joints comprise a ball on the connector and a socket for saidball in said coupling member.

6. The apparatus as described in claim 4 wherein each of said ball andsocket joints comprise a socket within the connector and a ball on saidcoupling member for said socket.

7. The apparatus as described in claim 1 wherein said expansioncompensating means comprises:

a. a first connector, one end of which is pivotally mounted to saidsecond extruder barrel;

b. a second connector, one end of which is pivotally mounted to saiddie-head; and

c. a coupling member coupling the other ends of said first and secondconnectors and being telescopically connected to at least one of saidconnectors.

8. The apparatus as described in claim 7 wherein the pivotal connectionsof said first and second connectors are ball joints.

9. The apparatus as described in claim 7 wherein said telescopicconnection comprises a sleeve and an inner tubular member arranged in aclose sliding fit within said sleeve and terminating therein, theterminating end of said inner member being beveled on the inside foroutward deflection from pressure within said inner tubular member andfor forming a pressure seal against the inner surface of said sleeve.

10. The apparatus as described in claim 1 wherein said first and secondextruder barrels are on opposite sides of said die-head.

11. The apparatus as described in claim 10 wherein said cross-head isadapted to receive a continuous core and for depositing said layers ofthermoplastic material on said core and wherein the innermost layer onsaid core is formed from material supplied from said first extruderbarrel.

1. Apparatus for extruding multiple layers of a thermoplastic materialcomprising: a. a die-head having dies for forming each of said layers;b. a first extruder barrel fixed to said die-head for supplyingthermoplastic material to said die-head at a first point; c. a secondextruder barrel for supplying thermoplastic material to said die-head ata second point; and d. thermal expansion compensating means connectingsaid second extruder barrel to said die-head to permit expansion alongthe longitudinal axis of said die-head.
 2. The apparatus as described inclaim 1 wherein said thermal expansion compensating means comprises: a.a first connector connected to said second extruder barrel; b. a secondconnector telescopicAlly mounted to said die-head; and c. a couplingmember pivotally connected at one end to said first connector and at itsother end to said second connector.
 3. The apparatus as described inclaim 2 wherein said telescopic connection comprises a sleeve and aninner tubular member arranged in a close sliding fit within said sleeveand terminating therein, the terminating end of said inner member beingbeveled on the inside for outward deflection from pressure within saidinner tubular member and for forming a pressure seal against the innersurface of said sleeve.
 4. The apparatus as described in claim 2 whereinthe pivotal connections for said coupling member are ball and socketjoints.
 5. The apparatus as described in claim 4 wherein each of saidball and socket joints comprise a ball on the connector and a socket forsaid ball in said coupling member.
 6. The apparatus as described inclaim 4 wherein each of said ball and socket joints comprise a socketwithin the connector and a ball on said coupling member for said socket.7. The apparatus as described in claim 1 wherein said expansioncompensating means comprises: a. a first connector, one end of which ispivotally mounted to said second extruder barrel; b. a second connector,one end of which is pivotally mounted to said die-head; and c. acoupling member coupling the other ends of said first and secondconnectors and being telescopically connected to at least one of saidconnectors.
 8. The apparatus as described in claim 7 wherein the pivotalconnections of said first and second connectors are ball joints.
 9. Theapparatus as described in claim 7 wherein said telescopic connectioncomprises a sleeve and an inner tubular member arranged in a closesliding fit within said sleeve and terminating therein, the terminatingend of said inner member being beveled on the inside for outwarddeflection from pressure within said inner tubular member and forforming a pressure seal against the inner surface of said sleeve. 10.The apparatus as described in claim 1 wherein said first and secondextruder barrels are on opposite sides of said die-head.
 11. Theapparatus as described in claim 10 wherein said cross-head is adapted toreceive a continuous core and for depositing said layers ofthermoplastic material on said core and wherein the innermost layer onsaid core is formed from material supplied from said first extruderbarrel.